Pakistan: Revenge for OBL and drone attacks? They can supply an entire, finished warhead for those medium range missiles or all of the parts and NK refines the fuel (with Pakistani help).
South Africa: used to have nukes, what happened to the bombs, blueprints, fuel and fuel processing equipment.
Russia: They wouldn't give NK anything nuclear, but seeing as how mothers and first born are for sale in Russia, anything is possible.
Iran: Joint venture with NK, and NK may be testing Iran's bomb design with this missile launch.
China: They let NK build up enough potential capability, perhaps NK's program got away from Beijing's control with the help of corrupt/rogue/nationalist PLA officers and scientists.
India: See Russia.
US: our computer security regarding our nuke warhead designs, as well as physical security. And its all the fault of foreign hackers, not our worthless CEO or internet security cadres.
It would be the height of tragic irony if NK had two warheads based on designs hacked from our defense establishment.
Libya: Chaos provides access to Chinese bomb tech
EU: They didn't have a problem equipping Iran